Electrical computers and digital data processing systems: input/ – Access arbitrating – Access prioritizing
Reexamination Certificate
1998-08-14
2001-08-28
Lefkowitz, Sumati (Department: 2181)
Electrical computers and digital data processing systems: input/
Access arbitrating
Access prioritizing
C714S031000
Reexamination Certificate
active
06282600
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to information processing systems and more particularly to a method and apparatus for acquiring and managing system data through a system JTAG port.
BACKGROUND OF THE INVENTION
Most current computer system designs utilize the concept of a service processor. The service processor is typically used to handle various “power-on” type functions, such as test, scan utilization, starting clocks, etc. Once the computer is “booted up” and begins to run, there are usually control or status registers that the system needs to set or interrogate. Also, as the topology of systems becomes more distributed, it becomes critical to access certain instrumented performance facilities or internal workload traces in order to maintain workload balancing across the entire system or to gather sequential snapshots of machines' states in real time. It is also critical that the accessing and usage of this performance monitoring data be non-invasive to normal workload processing.
Accordingly, there is a need for an enhanced method and apparatus which is effective to provide a service processor with access to a number of registers internal to a chip while system clocks are running and without imposing any restriction that the registers be connected in a unique scan string or common clock boundary.
SUMMARY OF THE INVENTION
A method and apparatus is provided by which a service processor is enabled to access system and chip registers to acquire system data through the use of the system JTAG bus. In one embodiment, logic is provided to determine concurrent calls for use of the same registers by both the system CPUs and also by the service processor through the JTAG bus, in which case the JTAG data are held so as not to interfere with system operations until the system's use of the register has been completed.
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Maule Warren Edward
Moore Roy Stuart
Victor David W.
Welbon Edward Hugh
International Business Machines - Corporation
Leeuwen Leslie A. Van
Lefkowitz Sumati
Wilder Robert V.
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